Solid-state imaging devices with impurity regions between photoelectric conversion regions and methods for manufacturing the same

ABSTRACT

Channel stop sections formed by multiple times of impurity ion implanting processes. Four-layer impurity regions are formed across the depth of a semiconductor substrate (across the depth of the bulk), so that a P-type impurity region is formed deep in the semiconductor substrate; thus, incorrect movement of electric charges is prevented. Other four-layer impurity regions of another channel stop section are decreased in width step by step across the depth of the substrate, so that the reduction of a charge storage region of a light receiving section due to the dispersion of P-type impurity in the channel stop section is prevented in the depth of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/309,346, filed Jun. 19, 2014, which is a continuation ofU.S. patent application Ser. No. 13/855,855, filed Apr. 3, 2013, nowU.S. Pat. No. 8,816,416, which is a continuation of U.S. patentapplication Ser. No. 13/348,733, filed Jan. 12, 2012, now U.S. Pat. No.8,431,976, which is a continuation of U.S. patent application Ser. No.12/537,829, filed Aug. 7, 2009, now U.S. Pat. No. 8,115,268, which is acontinuation of U.S. patent application Ser. No. 11/677,301, filed onFeb. 21, 2007, now U.S. Pat. No. 7,642,614, which is a division of U.S.patent application Ser. No. 10/705,552, filed Nov. 11, 2003, now U.S.Pat. No. 7,198,976, the entire disclosures of which are herebyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a solid-state imaging device formed byintegrating a plurality of photosensors on a substrate in which achannel stop section for preventing leakage of electric charges betweenthe photosensors can be effectively formed and to a method formanufacturing the same.

FIG. 6 is an explanatory view of an example of the arrangement of a CCDsolid-state imaging device.

The solid-state imaging device includes a photosensor (imaging region)410, a CCD vertical transfer section 420, a CCD horizontal transfersection 430, an output 440 and so on in a substrate 400.

The photosensor 410 has a plurality of the CCD vertical transfersections 420 along the respective photosensor trains, in which signalcharges stored by the photosensors 412 are output to the CCD verticaltransfer sections 420 and sequentially transferred in the verticaldirection by the driving of the CCD vertical transfer sections 420.

The CCD vertical transfer sections 420 have the CCD horizontal transfersection 430 at the end, in which the signal charges transferred from theCCD vertical transfer sections 420 are output to the CCD horizontaltransfer sections 430 line by line and sequentially transferred in thehorizontal direction by the driving of the CCD horizontal transfersections 430.

The output 440 receives the signal charges transferred by the CCDhorizontal transfer sections 430 by a floating diffusion (FD), sensesthe potential of the FD by an amp transistor, and converts it to anelectric signal for output.

The solid-state imaging device has a channel stop section for preventingcharge leakage between the pixels along the vertical transfer direction(along the column of the photosensors) and the photosensor and betweenthe photosensors along the horizontal transfer direction (along the rowof the photosensors) and the CCD vertical transfer section (for example,refer to Japanese Unexamined Patent Application Publication No.4-280675).

FIG. 7 is a sectional view of an embodiment of the channel stop sectionprovided between the photosensors along the vertical transfer direction,showing a section taken along line A-A of FIG. 6.

As shown in the drawing, a photodiode region constituting a photoreceiving section 510 of each photosensor has a P+ type impurity region510A formed in the outer layer of a substrate 400 and an N-type impurityregion 510B formed under the P+ type impurity region 510A.

Channel stop sections 520, or P-type impurity regions, are provided inthe vicinity of opposite sides of the photodiode region along thevertical transfer direction.

Although transfer electrodes 550 of the CCD vertical transfer sections420 and so on are provided on the top of the substrate 400 through agate insulating film (not shown), their detailed description will beomitted here because they are not directly related to the presentinvention.

FIG. 8 is a sectional view of an embodiment of the channel stop sectionprovided between a photosensor along the horizontal transfer directionand the vertical transfer section, showing a section taken along lineB-B of FIG. 6.

As shown in the drawing, the photodiode region of each photosensorincludes the P+ type impurity region 510A and the N-type impurity region510B, as that shown in FIG. 7.

The CCD vertical transfer section 420 is formed on the side of thephotodiode region through a readout gate.

The CCD vertical transfer section 420 is formed of an upper N-typeimpurity region 420A and a lower P-type impurity region 420B.

A channel stop section 520 that is a P-type impurity region is providedbetween the CCD vertical transfer section 420 and the photodiode regionof the adjacent photosensor train.

The above-described solid-state imaging device has a conspicuoustendency to reduce the space between the vertical and horizontalphotosensors with the reduction of the photosensor size owing toincreasing number of photosensors and advancement towardminiaturization.

Therefore, the structure of the related-art channel stop section that isformed only in the outer layer of the substrate has the problem of noteffectively preventing a phenomenon in which electric charges that arephotoelectrically converted in the photodiode region are mixed to theadjacent photosensors (hereinafter, referred to as a color mixingphenomenon).

In order to prevent the color mixing phenomenon, it is necessary toincrease energy during implantation of impurity ions to the channel stopsection to thereby form the channel stop section deep in the substrate(along the depth of the bulk). However, when ions are implanted withhigh energy, the P-type impurity near the surface declines inconcentration and so a smear component in the surface of the substratecannot be reduced, leading an adverse smear phenomenon.

The ion plantation with high energy has the problem of easily causingdispersion of the P-type impurity, narrowing a charge storage region ofthe light receiving section (photodiode region), which decreasessensitivity and saturation signals.

BACKGROUND OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod for manufacturing a solid-state imaging device that provides ahigh quality image by forming a channel stop section that is effectivein miniaturization of photosensors to prevent a color mixing phenomenonand so on.

By a method for manufacturing a solid-state imaging device, according tothe present invention, a channel stop section is formed by multipletimes of ion implantation with multiple implanting energies. Thus, amultilayer impurity region can be formed across the depth of a substrateto form a channel stop section.

Therefore, the leakage of signal charges between adjacent photosensorsand between a photosensor and a transfer section can be effectivelyprevented; thus, a color mixing phenomenon can be effectively prevented.

Since multiple times of ion implantation are made for multipleimplantation areas during multiple times of impurity ion implantingprocesses, the dispersion of impurity particularly deep in the substratecan be prevented, effects to a photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Since the multiple times of ion implantation are made at multiple ionconcentrations during multiple times of impurity ion implantingprocesses, the impurity regions of the respective layers of the channelstop section can be given optimum impurity concentration; thus,anti-smear measures on the surface of the substrate can be effectivelytaken.

Since a solid-state imaging device according to the invention includes achannel stop section having multiple layers across the depth of thesubstrate, the leakage of signal charges between adjacent photosensorsand between a photosensor and a transfer section can be effectivelyprevented; thus, a color mixing phenomenon can be effectively prevented.

Since the areas of the multiple layers of the channel stop section aremultiple, the dispersion of impurity particularly deep in the substratecan be prevented, effects to a photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Furthermore, since the ion concentrations of the multiple layers of thechannel stop section are optimum, anti-smear measures on the surface ofthe substrate can be effectively taken.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod for manufacturing a solid-state imaging device that provides ahigh quality image by forming a channel stop section that is effectivein miniaturization of photosensors to prevent a color mixing phenomenonand so on.

By a method for manufacturing a solid-state imaging device, according tothe present invention, a channel stop section is formed by multipletimes of ion implantation with multiple implanting energies. Thus, amultilayer impurity region can be formed across the depth of a substrateto form a channel stop section.

Therefore, the leakage of signal charges between adjacent photosensorsand between a photosensor and a transfer section can be effectivelyprevented; thus, a color mixing phenomenon can be effectively prevented.

Since multiple times of ion implantation are made for multipleimplantation areas during multiple times of impurity ion implantingprocesses, the dispersion of impurity particularly deep in the substratecan be prevented, effects to a photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Since the multiple times of ion implantation are made at multiple ionconcentrations during multiple times of impurity ion implantingprocesses, the impurity regions of the respective layers of the channelstop section can be given optimum impurity concentration; thus,anti-smear measures on the surface of the substrate can be effectivelytaken.

Since a solid-state imaging device according to the invention includes achannel stop section having multiple layers across the depth of thesubstrate, the leakage of signal charges between adjacent photosensorsand between a photosensor and a transfer section can be effectivelyprevented; thus, a color mixing phenomenon can be effectively prevented.

Since the areas of the multiple layers of the channel stop section aremultiple, the dispersion of impurity particularly deep in the substratecan be prevented, effects to a photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Furthermore, since the ion concentrations of the multiple layers of thechannel stop section are optimum, anti-smear measures on the surface ofthe substrate can be effectively taken.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a solid-state imaging device along thevertical direction according to an embodiment of the present invention;

FIG. 2 is a sectional view of the solid-state imaging device along thehorizontal direction according to the embodiment of the presentinvention;

FIG. 3 is a sectional view of a solid-state imaging device along thevertical direction according to another embodiment of the presentinvention;

FIG. 4 is a sectional view of a solid-state imaging device along thevertical direction according to yet another embodiment of the presentinvention;

FIG. 5 is a sectional view of a solid-state imaging device along thevertical direction according to still another embodiment of the presentinvention;

FIG. 6 is a plan view of the arrangement of a CCD solid-state imagingdevice;

FIG. 7 is a sectional view of a related-art solid-state imaging devicealong the vertical direction; and

FIG. 8 is a sectional view of the related-art solid-state imaging devicealong the horizontal direction.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of a solid-state imaging device and a method formanufacturing the same according to the present invention will bespecifically described hereinafter.

FIGS. 1 and 2 are sectional views of a solid-state imaging devicemanufactured by the method according to an embodiment, FIG. 1 showing anembodiment of a channel stop section provided between photosensors alongthe vertical transfer direction, and FIG. 2 showing an embodiment of achannel stop section provided between the photosensors along thehorizontal transfer direction. The entire structure of the solid-stateimaging device is the same as that of the related art shown in FIG. 6,wherein FIG. 1 corresponds to the section taken along line A-A of FIG. 6and FIG. 2 corresponds to the section taken along line B-B of FIG. 6.

Referring first to FIG. 1, a photodiode region constituting a lightreceiving section 10 of each photosensor includes a P+ type impurityregion (hole storage region) 10A formed in the outer layer of asubstrate 100 and an N-type impurity region (electron storage region)10B formed under the P+-type impurity region 10A. The photodiode regionphotoelectrically converts light that is incident from above, absorbsholes into the P+ type impurity region 10A, and stores electrons in theN-type impurity region 10B, a lower depletion layer and so on.

The photoelectric conversion in the light receiving section 10 is mainlyperformed in a depletion region between the N-type impurity region 10Band the P+ type impurity region 10A and in a depletion region betweenthe N-type impurity region 10B and a lower P-type impurity region (notshown).

A channel stop section 20 formed of a multilayer P-type impurity regionis provided in the vicinity of opposite

sides of the photodiode region along the vertical transfer direction.

The channel stop section 20 is formed by multiple times of impurityimplanting processes by which four impurity regions 20A, 20B, 20C, and20D are formed across the depth of the substrate 100 (along the depth ofthe bulk) to form a P-type region deep in the substrate 100, therebypreventing leakage of electric charges.

Referring to FIG. 2, the photodiode region of each photosensor includesthe P+ type impurity region 10A and the N-type impurity region 10B, asthat shown in FIG. 1.

A CCD vertical transfer section 40 is formed on the side of thephotodiode region through a readout gate.

The CCD vertical transfer section 40 is formed of an upper N-typeimpurity region 40A and a lower P-type impurity region 40B.

A channel stop section 50 that is a multilayer P-type impurity region isprovided between the CCD vertical transfer section 40 and the photodioderegion of the adjacent photosensor train.

The channel stop section 50 is formed by multiple times of impurityimplanting processes by which four impurity regions 50A, 50B, 50C, and50D are formed across the depth of the substrate 100 (along the depth ofthe bulk) to form a

P-type region deep in the substrate 100, thereby preventing leakage ofelectric charges.

In FIGS. 1 and 2, transfer electrodes 60 of the CCD vertical transfersections 40 and so on are provided on the top of the substrate 100through a gate insulating film (not shown). However, their detaileddescription will be omitted here because they are not directly relatedto the present invention.

When the channel stop sections 20 and 50 are formed in theabove-described solid-state imaging device, an ion implantation regionis set using a specified mask and multiple times of ion implantingprocesses are performed with multiple ion implanting energies andimpurity concentrations, so that the multilayer impurity regions 20A,20B, 20C, and 20D and the impurity regions 50A, 50B, 50C, and 50D areformed.

Thus, the channel stop sections 20 and 50 can be formed deep into thesubstrate 100, thereby preventing the leakage of signal charges betweenthe devices to reduce color mixture.

Since the concentration of impurity in each ion implanting process canbe set as appropriate, the concentration of impurity near the surface ofthe substrate 100 that is formed with low implanting energy can besufficiently ensured by making the ion concentration of impurity in anion implanting process with relatively high implanting energy higherthan that in an ion implanting process with relatively low implantingenergy, so that a smear phenomenon can be prevented.

When the solid-state imaging device is formed, ions are continuouslyimplanted into the substrate 100 to form the photodiode region (lightreceiving section 10), the CCD vertical transfer section 40, and therespective impurity regions of the channel stop sections 20 and 50; theorder thereof is not particularly limited.

Also the order of the multiple times of ion implanting processes forforming the channel stop sections 20 and 50 is not particularly limited.

The mask for ion implantation includes various types in addition to ageneral resist mask; therefore, it is not particularly limited.

A specific energy and the concentration of impurity in each ionimplanting process can be set as appropriate and are not particularlylimited.

In the embodiment, the vertical channel stop section 20 and thehorizontal channel stop section 50 are separately formed so as to beoptimized for the respective required characteristics, with individualion implanting energy and impurity concentration. In FIGS. 1 and 2,although both the channel stop sections 20 and 50 have four-layerstructure (or four-step ion implantation), they are not limited to thatand may have a structure other than the four-layer (four-step)structure. The vertical channel stop section 20 and the horizontalchannel stop section 50 may not necessarily have the same number oflayers.

The impurity concentration may not be varied at all the layers but maybe varied at part of the layers.

In the above embodiment, the ion implanting processes for forming thechannel stop sections 20 and 50 are carried out with multiple energiesand concentrations. However, the ion implantation region is varied ineach ion implanting process by changing a mask in each ion implantingprocess, so that the width across the channel of the respective impurityregions of the channel stop sections 20 and 50 may be varied.

FIG. 3 is a sectional view of an example of the channel stop sectionalong the vertical transfer direction. Since components other than achannel stop section 70 are the same as those of FIG. 1, they are giventhe same numerals and there description will be omitted.

As shown in the drawing, the channel stop section 70 includes four-layerimpurity regions 70A, 70B, 70C, and 70D. When the ion implanting area inan ion implanting process with relatively high implanting energy is madesmaller than that in an ion implanting process with relatively lowimplanting energy, the reduction of the charge storage region of thelight receiving section 10 in the deep part of the substrate 100 by thedispersion of P-type impurity of the channel stop section 70 can beprevented; thus, sensitivity of the light receiving section 10 andsaturation signals can be increased.

The energy and the impurity concentration can be set as those in FIG. 1.

Although the widths of all the layers of the channel stop section 70 maybe varied, only the width of part of the layers may be varied so thatonly the impurity regions 70A and 70B have the equal width, as shown inFIG. 3. In this case, the layers of an equal width can be formed with acommon mask.

The multi-step ion implantation may also be made for the channel stopsection along the horizontal transfer direction, with multiple widths.

The above-described embodiments offer the following advantages:

(1) Referring to FIGS. 1 to 3, when multi-step ion implantation of thechannel stop section between the vertical photosensors and the channelstop section between the horizontal light receiving section and thevertical transfer section is carried out with multiple energies, a colormixing phenomenon can be prevented in which photoelectrically convertedcharges are mixed to the adjacent photosensors.

(2) Referring to FIG. 3, when the region of ion implantation with highenergy reduced, a color mixing phenomenon can be prevented withoutnarrowing the charge storage region of the light receiving section anddecreasing sensitivity and saturation signal.

(3) Referring to FIGS. 1 to 3, when ions are implanted into the channelstop section with high energy, the variation of an overflow barrier atcharge storage can be reduced; thus the occurrence of a knee-point(Qknee) in output characteristics can be prevented.

(4) When ion implantation of the channel stop section between thehorizontal light receiving section and the vertical transfer section iscarried out with multiple energies, a smear phenomenon near the surfaceand in the bulk can be prevented.

In the above-described embodiments, the positional relationship of themulti-step ion implanted impurity regions is only an example, and thethickness of the impurity regions across the depth of the substrate, theshape, and the number of layers are not limited to that. For example, asshown in FIG. 4, of the multilayer impurity region of a channel stopsection 80 (three-layer impurity regions 80A, 80B, and 80C in thedrawing), the middle-layer impurity region (the impurity region 80B inthe drawing) may

be larger in thickness and also in lateral width than the other impurityregions or vice versa.

As a matter of course, the multilayer ion-implanted impurity region mayhave a part overlapping with the upper and lower impurity regions in thestrict sense.

In the above embodiments, although the multilayer ion-implanted impurityregion is formed such that the bottom of the lowermost-layer region hasa depth substantially equal to that of the bottom of the N-type impurityregion 10B in the light receiving section 10, it is not limited to that.

For example, in order to prevent color mixture in a further lower regionacross the depth of the substrate 100, as shown in FIG. 5, the bottom ofthe lowermost-layer region (an impurity region 90D in the drawing) ofthe multilayer ion-implanted impurity region (four-layer impurityregions 90A, 90B, 90C, and 90D in the drawing) of a channel stop section90 may be formed deeper than the bottom of the N-type impurity region10B.

As shown in FIG. 5, an overflow barrier 92 located below the lightreceiving section 10 and the multilayer ion-implanted impurity region(the impurity region 90D in the drawing) may be in contact with eachother.

In this case, the holes stored in the overflow barrier 92 can bedischarged to the surface of the substrate 100 through the multilayerion-implanted impurity region. The multilayer ion-implanted impurityregion is preferably formed such that the closer to the surface of thesubstrate 100 the region is, the higher the concentration of the P-typeimpurity is.

Although a preferred form of the invention has been described in whichit is applied to a CCD solid-state imaging device, it is to beunderstood that the invention is applied not only to the CCD solid-stateimaging device but also to a CMOS solid-state imaging device.

As described above, by the method for manufacturing the solid-stateimaging device according to the invention, the channel stop section isformed by multiple times of impurity ion implanting processes withmultiple implanting energies. Thus, a multilayer impurity region can beformed across the depth of the substrate as a channel stop section.

Therefore, leakage of signal charges between the adjacent photosensorsand between the photosensor and the transfer section can be effectivelyprevented, so that a color mixing phenomenon and so on can beeffectively prevented.

During the multiple times of impurity ion-implantation processes, theion implantation is carried out for multiple implantation areas, so thatthe dispersion of the impurity can be reduced particularly deep in thesubstrate, the effects to the photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Furthermore, during the multiple times of impurity ion-implantationprocesses, the ion implantation is carried out at multiple impurityconcentrations, so that the respective impurity regions of the channelstop section can be formed at optimum impurity concentrations; thusanti-smear measures on the surface of the substrate can be effectivelytaken.

Since the solid-state imaging device according to the invention includesa channel stop section having a multilayer impurity region across thedepth of the substrate, leakage of signal charges between the adjacentphotosensors and between the photosensor and the transfer section can beeffectively prevented; thus, a color mixing phenomenon and so on can beeffectively prevented.

Since the multilayer impurity region of the channel stop section hasmultiple areas, the dispersion of impurity particularly deep in thesubstrate can be prevented, the effects to the photoelectric conversionsection can be reduced, and decreases in sensitivity and saturationsignals can be effectively prevented.

Furthermore, the multilayer impurity region of the channel stop sectionhas an optimum impurity concentration at each layer; thus anti-smearmeasures on the surface of the substrate can be effectively taken.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a solid-state imaging device along thevertical direction according to an embodiment of the present invention;

FIG. 2 is a sectional view of the solid-state imaging device along thehorizontal direction according to the embodiment of the presentinvention;

FIG. 3 is a sectional view of a solid-state imaging device along thevertical direction according to another embodiment of the presentinvention;

FIG. 4 is a sectional view of a solid-state imaging device along thevertical direction according to yet another embodiment of the presentinvention;

FIG. 5 is a sectional view of a solid-state imaging device along thevertical direction according to still another embodiment of the presentinvention;

FIG. 6 is a plan view of the arrangement of a CCD solid-state imagingdevice;

FIG. 7 is a sectional view of a related-art solid-state imaging devicealong the vertical direction; and

FIG. 8 is a sectional view of the related-art solid-state imaging devicealong the horizontal direction.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of a solid-state imaging device and a method formanufacturing the same according to the present invention will bespecifically described hereinafter.

FIGS. 1 and 2 are sectional views of a solid-state imaging devicemanufactured by the method according to an embodiment, FIG. 1 showing anembodiment of a channel stop section provided between photosensors alongthe vertical transfer direction, and FIG. 2 showing an embodiment of achannel stop section provided between the photosensors along thehorizontal transfer direction. The entire structure of the solid-stateimaging device is the same as that of the related art shown in FIG. 6,wherein FIG. 1 corresponds to the section taken along line A-A of FIG. 6and FIG. 2 corresponds to the section taken along line B-B of FIG. 6.

Referring first to FIG. 1, a photodiode region constituting a lightreceiving section 10 of each photosensor includes a P+ type impurityregion (hole storage region) 10A formed in the outer layer of asubstrate 100 and an N-type impurity region (electron storage region)10B formed under the P+-type impurity region 10A. The photodiode regionphotoelectrically converts light that is incident from above, absorbsholes into the P+ type impurity region 10A, and stores electrons in theN-type impurity region 10B, a lower depletion layer and so on.

The photoelectric conversion in the light receiving section 10 is mainlyperformed in a depletion region between the N-type impurity region 10Band the P+ type impurity region 10A and in a depletion region betweenthe N-type impurity region 10B and a lower P-type impurity region (notshown).

A channel stop section 20 formed of a multilayer P-type impurity regionis provided in the vicinity of opposite

sides of the photodiode region along the vertical transfer direction.

The channel stop section 20 is formed by multiple times of impurityimplanting processes by which four impurity regions 20A, 20B, 20C, and20D are formed across the depth of the substrate 100 (along the depth ofthe bulk) to form a P-type region deep in the substrate 100, therebypreventing leakage of electric charges.

Referring to FIG. 2, the photodiode region of each photosensor includesthe P+ type impurity region 10A and the N-type impurity region 10B, asthat shown in FIG. 1.

A CCD vertical transfer section 40 is formed on the side of thephotodiode region through a readout gate.

The CCD vertical transfer section 40 is formed of an upper N-typeimpurity region 40A and a lower P-type impurity region 40B.

A channel stop section 50 that is a multilayer P-type impurity region isprovided between the CCD vertical transfer section 40 and the photodioderegion of the adjacent photosensor train.

The channel stop section 50 is formed by multiple times of impurityimplanting processes by which four impurity regions 50A, 50B, 50C, and50D are formed across the depth of the substrate 100 (along the depth ofthe bulk) to form a

P-type region deep in the substrate 100, thereby preventing leakage ofelectric charges.

In FIGS. 1 and 2, transfer electrodes 60 of the CCD vertical transfersections 40 and so on are provided on the top of the substrate 100through a gate insulating film (not shown). However, their detaileddescription will be omitted here because they are not directly relatedto the present invention.

When the channel stop sections 20 and 50 are formed in theabove-described solid-state imaging device, an ion implantation regionis set using a specified mask and multiple times of ion implantingprocesses are performed with multiple ion implanting energies andimpurity concentrations, so that the multilayer impurity regions 20A,20B, 20C, and 20D and the impurity regions 50A, 50B, 50C, and 50D areformed.

Thus, the channel stop sections 20 and 50 can be formed deep into thesubstrate 100, thereby preventing the leakage of signal charges betweenthe devices to reduce color mixture.

Since the concentration of impurity in each ion implanting process canbe set as appropriate, the concentration of impurity near the surface ofthe substrate 100 that is formed with low implanting energy can besufficiently ensured by making the ion concentration of impurity in anion implanting process with relatively high implanting energy higherthan that in an ion implanting process with relatively low implantingenergy, so that a smear phenomenon can be prevented.

When the solid-state imaging device is formed, ions are continuouslyimplanted into the substrate 100 to form the photodiode region (lightreceiving section 10), the CCD vertical transfer section 40, and therespective impurity regions of the channel stop sections 20 and 50; theorder thereof is not particularly limited.

Also the order of the multiple times of ion implanting processes forforming the channel stop sections 20 and 50 is not particularly limited.

The mask for ion implantation includes various types in addition to ageneral resist mask; therefore, it is not particularly limited.

A specific energy and the concentration of impurity in each ionimplanting process can be set as appropriate and are not particularlylimited.

In the embodiment, the vertical channel stop section 20 and thehorizontal channel stop section 50 are separately formed so as to beoptimized for the respective required characteristics, with individualion implanting energy and impurity concentration. In FIGS. 1 and 2,although both the channel stop sections 20 and 50 have four-layerstructure (or four-step ion implantation), they are not limited to thatand may have a structure other than the four-layer (four-step)structure. The vertical channel stop section 20

and the horizontal channel stop section 50 may not necessarily have thesame number of layers.

The impurity concentration may not be varied at all the layers but maybe varied at part of the layers.

In the above embodiment, the ion implanting processes for forming thechannel stop sections 20 and 50 are carried out with multiple energiesand concentrations. However, the ion implantation region is varied ineach ion implanting process by changing a mask in each ion implantingprocess, so that the width across the channel of the respective impurityregions of the channel stop sections 20 and 50 may be varied.

FIG. 3 is a sectional view of an example of the channel stop sectionalong the vertical transfer direction. Since components other than achannel stop section 70 are the same as those of FIG. 1, they are giventhe same numerals and there description will be omitted.

As shown in the drawing, the channel stop section 70 includes four-layerimpurity regions 70A, 70B, 70C, and 70D. When the ion implanting area inan ion implanting process with relatively high implanting energy is madesmaller than that in an ion implanting process with relatively lowimplanting energy, the reduction of the charge storage region of thelight receiving section 10 in the deep part of the substrate 100 by thedispersion of P-type impurity of the channel stop section 70 can beprevented; thus, sensitivity of the light receiving section 10 andsaturation signals can be increased.

The energy and the impurity concentration can be set as those in FIG. 1.

Although the widths of all the layers of the channel stop section 70 maybe varied, only the width of part of the layers may be varied so thatonly the impurity regions 70A and 70B have the equal width, as shown inFIG. 3. In this case, the layers of an equal width can be formed with acommon mask.

The multi-step ion implantation may also be made for the channel stopsection along the horizontal transfer direction, with multiple widths.

The above-described embodiments offer the following advantages:

(1) Referring to FIGS. 1 to 3, when multi-step ion implantation of thechannel stop section between the vertical photosensors and the channelstop section between the horizontal light receiving section and thevertical transfer section is carried out with multiple energies, a colormixing phenomenon can be prevented in which photoelectrically convertedcharges are mixed to the adjacent photosensors.

(2) Referring to FIG. 3, when the region of ion implantation with highenergy reduced, a color mixing phenomenon can be prevented withoutnarrowing the charge storage region of the light receiving section anddecreasing sensitivity and saturation signal.

(3) Referring to FIGS. 1 to 3, when ions are implanted into the channelstop section with high energy, the variation of an overflow barrier atcharge storage can be reduced; thus the occurrence of a knee-point(Qknee) in output characteristics can be prevented.

(4) When ion implantation of the channel stop section between thehorizontal light receiving section and the vertical transfer section iscarried out with multiple energies, a smear phenomenon near the surfaceand in the bulk can be prevented.

In the above-described embodiments, the positional relationship of themulti-step ion implanted impurity regions is only an example, and thethickness of the impurity regions across the depth of the substrate, theshape, and the number of layers are not limited to that. For example, asshown in FIG. 4, of the multilayer impurity region of a channel stopsection 80 (three-layer impurity regions 80A, 80B, and 80C in thedrawing), the middle-layer impurity region (the impurity region 80B inthe drawing) may be larger in thickness and also in lateral width thanthe other impurity regions or vice versa.

As a matter of course, the multilayer ion-implanted impurity region mayhave a part overlapping with the upper and lower impurity regions in thestrict sense.

In the above embodiments, although the multilayer ion-implanted impurityregion is formed such that the bottom of the lowermost-layer region hasa depth substantially equal to that of the bottom of the N-type impurityregion 10B in the light receiving section 10, it is not limited to that.

For example, in order to prevent color mixture in a further lower regionacross the depth of the substrate 100, as shown in FIG. 5, the bottom ofthe lowermost-layer region (an impurity region 90D in the drawing) ofthe multilayer ion-implanted impurity region (four-layer impurityregions 90A, 90B, 90C, and 90D in the drawing) of a channel stop section90 may be formed deeper than the bottom of the N-type impurity region10B.

As shown in FIG. 5, an overflow barrier 92 located below the lightreceiving section 10 and the multilayer ion-implanted impurity region(the impurity region 90D in the drawing) may be in contact with eachother.

In this case, the holes stored in the overflow barrier 92 can bedischarged to the surface of the substrate 100 through the multilayerion-implanted impurity region. The multilayer ion-implanted impurityregion is preferably formed such that the closer to the surface of thesubstrate 100 the region is, the higher the concentration of the P-typeimpurity is.

Although a preferred form of the invention has been described in whichit is applied to a CCD solid-state imaging device, it is to beunderstood that the invention is applied not only to the CCD solid-stateimaging device but also to a CMOS solid-state imaging device.

As described above, by the method for manufacturing the solid-stateimaging device according to the invention, the channel stop section isformed by multiple times of impurity ion implanting processes withmultiple implanting energies. Thus, a multilayer impurity region can beformed across the depth of the substrate as a channel stop section.

Therefore, leakage of signal charges between the adjacent photosensorsand between the photosensor and the transfer section can be effectivelyprevented, so that a color mixing phenomenon and so on can beeffectively prevented.

During the multiple times of impurity ion-implantation processes, theion implantation is carried out for multiple implantation areas, so thatthe dispersion of the impurity can be reduced particularly deep in thesubstrate, the effects to the photoelectric conversion section can bereduced, and decreases in sensitivity and saturation signals can beeffectively prevented.

Furthermore, during the multiple times of impurity ion-implantationprocesses, the ion implantation is carried out at multiple impurityconcentrations, so that the respective impurity regions of the channelstop section can be formed at optimum impurity concentrations; thusanti-smear measures on the surface of the substrate can be effectivelytaken.

Since the solid-state imaging device according to the invention includesa channel stop section having a multilayer impurity region across thedepth of the substrate, leakage of signal charges between the adjacentphotosensors and between the photosensor and the transfer section can beeffectively prevented; thus, a color mixing phenomenon and so on can beeffectively prevented.

Since the multilayer impurity region of the channel stop section hasmultiple areas, the dispersion of impurity particularly deep in thesubstrate can be prevented, the effects to the photoelectric conversionsection can be reduced, and decreases in sensitivity and saturationsignals can be effectively prevented.

Furthermore, the multilayer impurity region of the channel stop sectionhas an optimum impurity concentration at each layer; thus anti-smearmeasures on the surface of the substrate can be effectively taken.

While various embodiments of the present invention have been described,it will be apparent to those of skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention. Accordingly, the present invention is not to berestricted except in light of the attached claims and their equivalents.

What is claimed is:
 1. An imaging device comprising: a semiconductorsubstrate having a first side and a second side opposite to the firstside; a first photoelectric conversion region and a second photoelectricconversion region disposed in the semiconductor substrate; a transferelectrode adjacent to the first side of the semiconductor substrate; anda first impurity region and a second impurity region in thesemiconductor substrate; wherein, the first and second impurity regionsare between the first photoelectric conversion region and the secondphotoelectric conversion region, the first and second photoelectricconversion regions include an N-type impurity region, the first andsecond impurity regions include a P-type impurity region, the secondimpurity region is closer to the second side of the semiconductorsubstrate than the first impurity region, and a cross-sectional area ofthe first impurity region is larger than a cross-sectional area of thesecond impurity region.
 2. The imaging device according to claim 1,further comprising a third impurity region associated with the secondimpurity region along a direction of increasing depth of thesemiconductor substrate, wherein when viewed in the direction ofincreasing depth of the semiconductor substrate, a cross-sectional areaof the third impurity region is smaller than a cross-sectional area ofthe second impurity region.
 3. The imaging device according to claim 1,wherein each of the impurity regions, when viewed in a direction ofincreasing depth of the semiconductor substrate, has a generally uniformcross-sectional area that is different for at least two of the impurityregions.
 4. The imaging device according to claim 2, wherein each of theimpurity regions, when viewed in a direction of increasing depth of thesemiconductor substrate, has a generally uniform cross-sectional areathat is different for at least two of the impurity regions.
 5. Theimaging device according to claim 3, wherein, for each of the impurityregions in the direction of increasing depth of the semiconductorsubstrate, the generally uniform cross-sectional area is less than thatof a preceding adjoining impurity region.
 6. The imaging deviceaccording to claim 2, wherein each of the impurity regions, when viewedin the direction of increasing depth of the semiconductor substrate, hasa generally uniform cross-sectional area and wherein, for each of theimpurity regions in the direction of increasing depth of thesemiconductor substrate, the generally uniform cross-sectional area isless than that of a preceding adjoining impurity region.
 7. The imagingdevice according to claim 1, wherein each of the impurity regions, whenviewed in a direction of increasing depth of the semiconductorsubstrate, has a generally uniform cross-sectional area equal to thegenerally uniform cross-sectional area of each other impurity region ofthe plurality of adjoining impurity regions.
 8. The imaging deviceaccording to claim 1, further comprising a third impurity regionassociated with the second impurity region along a direction ofincreasing depth of the semiconductor substrate, wherein each of theimpurity regions, when viewed in the direction of increasing depth ofthe semiconductor substrate, has a generally uniform cross-sectionalarea equal to the generally uniform cross-sectional area of each otherimpurity region of the plurality of adjoining impurity regions.
 9. Theimaging device according to claim 1, wherein each of the impurityregions has an ion concentration different from the ion concentration ofat least one other impurity region.
 10. The imaging device according toclaim 2, wherein each of the impurity regions has an ion concentrationdifferent from the ion concentration of at least one other impurityregion.
 11. The imaging device according to claim 1, wherein the imagingdevice is a CCD imaging device.
 12. The imaging device according toclaim 1, wherein the imaging device is a CMOS imaging device.
 13. Animaging device comprising: a semiconductor substrate having a first sideand a second side opposite to the first side; a first photoelectricconversion region and a second photoelectric conversion region disposedin the semiconductor substrate; a transfer electrode disposed adjacentto the first side of the semiconductor substrate; a first impurityregion and a second impurity region disposed in the semiconductorsubstrate; and an overflow barrier disposed in the semiconductorsubstrate; wherein, the first and second impurity regions are in contactwith the overflow barrier, the first and second impurity regions aredisposed between the first photoelectric conversion region and thesecond photoelectric conversion region, the first and secondphotoelectric conversion regions include an N-type impurity region, thefirst and second impurity regions include a P-type impurity region, thesecond impurity region is closer to the second side of the semiconductorsubstrate than the first impurity region, and a cross-sectional area ofthe first impurity region is larger than a cross-sectional area of thesecond impurity region.
 14. The imaging device according to claim 13,further comprising a third impurity region associated with the secondimpurity region along a direction of increasing depth of thesemiconductor substrate, wherein the cross-sectional area of the thirdimpurity region is smaller than a cross-sectional area of the secondimpurity region.
 15. The imaging device according to claim 13, whereineach of the impurity regions, when viewed in a direction of increasingdepth of the semiconductor substrate, has a generally uniformcross-sectional area that is different for at least two of the impurityregions.
 16. The imaging device according to claim 13, wherein each ofthe impurity regions, when viewed in a direction of increasing depth ofthe semiconductor substrate, has a generally uniform cross-sectionalarea equal to the generally uniform cross-sectional area of each otherimpurity region.
 17. The imaging device according to claim 13, whereineach of the impurity regions has an ion concentration different from theion concentration of at least one other impurity region.
 18. The imagingdevice according to claim 13, wherein the imaging device is a CCDimaging device.
 19. The imaging device according to claim 13, whereinthe imaging device is a CMOS imaging device.
 20. The imaging deviceaccording to claim 13, further comprising a third impurity regionassociated with the second impurity region along a direction ofincreasing depth of the semiconductor substrate, wherein each successiveimpurity region of the impurity regions in the direction of increasingdepth of the semiconductor substrate has a generally uniformcross-sectional area that is less than that of a preceding adjoiningimpurity region.